Method of forming piston rings



Feb. 23, 1943.

3'. A. BOWERS METHOD OF FORMING PISTON RINGS v4 Sheets-Sheet 1 Filed March 28, 1940 INVENTORI ATTORNEY Feb. 23, 1.943. BQWERS 2,311,728

METHOD OF FORMING P ISTON RINGS INVENTOR ATTORNEY T. A. BOWERS METHOD OF FORMING PISTON RINGS Feb, 23, 1943.

4 Sheets-Sheet 3 Filed March 28, 1940 INVENTOR BY (Z/1W6. Bow WWW ATTORNEY Feb. 23, 1943. T. A. BOWERS 2,311,728

METHOD OF FORMING PISTON RINGS Filed March 28, 1940 4 'Sheets-Sheet 4 ghee Ma; em

?atented Feb. 23, 1943 METHOD OF FORMING PISTON RINGS Thomas A. Bowers, Boston, Mass, assignor to Power Research Corporation, Boston, Mass, a corporation of Massachusetts Application March 28, 1940, Serial No. 326,340

1 Claim. (01. 29-1566) This invention relates to piston rings and more especially to methods of making piston rings of sheet materials.

It is a chief object of the invention to improve methods of making piston rings and to devise methods of fabricating from sheet materials composite structures generally adapted to comprising piston rings, and in particular oil control piston rings. A further object of the invention is to present methods of making novel ring portions and ring surfaces, and of imparting novel char acteristics to piston rings. The invention also aims to indicate generally methods of making piston rings which may be carried out with conventional tool machinery such as punches, dies, and the like, whereby the expense of designing and making special machinery is avoided and the cost of manufacture of piston rings is reduced.

The nature of the invention and its objects will more fully appear in the following description of the drawings and discussion relating thereto.

In the accompanying drawings:

Fig. 1 is a fragmentary plan view of sheet material which may be employed in manufacturing piston rings.

Fig. 2 is a fragmentary plan view of the material, illustrating a forming step in the method of making piston rings.

Fig. 3 is another plan view illustrating a further forming step.

Fig. 4 is a plan view illustrating a modified forming operation effected on sheet material.

Fig. 5 is a fragmentary perspective view illustrating a further step in the method relating to folding the formed material indicated in Fig. 3.

Fig. 6 is a fragmentary perspective view of a finished ring as viewed from the outside thereof.

Fig. 7 is a symmetrical cross section of the finished ring assembled in a piston groove.

Fig. 8 is a fragmentary plan view of-the ring.

Fig. 9 is a symmetrical cross sectional view of a ring similar to that shown in Figs. 5-8, inclusive, illustrating a further forming step.

Fig. 10 is an assembly view illustrating a preferred arrangement of rings of the type indicated in Fig. 9.

Figs. 11 and 12 illustrate modifications in the method of making piston rings indicated in Figs. l-6, inclusive.

Figs. 13-16, inclusive, illustrate another general type of method for making a piston ring construction from sheet metal material.

Figs. 17-21, inclusive, illustrate modifications in the method indicated in Figs. 13-16, inclusive.

Fig. 22 is a perspective view illustrating a modimethod indicated in Figs. 26-32, inclusive.

Referring in detail to the drawings, there have been illustrated a number of methods of treating sheet material which are directed to improving piston rings generally and in particular 011 metering piston rings. of the methods disclosed, Figs. 1-12, inclusive, relate to one general type of method and its modifications; Figs. 13-25, inclusive, indicate another type of method and its modifications; and Figs. 26-35, inclusive, illustrate still another type of method and modifications thereto.

Having reference to the construction included in Figs. 1-8, inclusive, numeral l denotes a length of sheet material employed in constructing the rings of the invention. The sheet material is of a resilient character and may consist of a spring steel, alloy, or other metal or suitable substance. According to the invention, a strip or sheet'oi the resilient material is formed in some desired manner to provide ring-forming portions and the material is folded in relation to these portions to provide desirable ring surfaces. As illustrated in Figs. 3 and 4, the strip l is punched to provide openings 2 occurring transversely within the strip and .to form web portions 3. At the edges of the strip are additional cuts or slits l and 5 which, along either edge, connect with every other opening 2. It will be noted that the cuts 4 along one edge are sta ered with relation to the cuts 5 along the opposite edge, with the result that there are provided segments or crown portions 6 and 1 occurring also in staggered relationship at opposite edges of the strip. The formed material is folded upon itself longitudinally of the strip as illustrated in Fig. 5. This provides a straight length of material which is formed into an annular body as illustrated in Figs. 6 and 8.

Thereafter a length of the material suitable for effecting a desired piston ring size is cut of! and various grinding or other conventional finishing operations may be resorted to, to provide a completed ring well suited to constituting an oil metering member.

The operations described in connection with treating the sheet material may be effected by apparatus commonl referred to as tool machinery." For example, the punching of opening 2 may readily be effected with conventional punch press mechanism. Similarly, the cutting of slits or openings 4 and can be effected by conventional cutting or shearing dies, and fold-' ing of the material achieved with the aid of conventional press mechanism or rolling means. Forming a straight length of folded material into a circular body can be effected in several ways, one example of which is to force a length of the material through an annular channel or die.

In the construction indicated there is provided an annular supporting structure made up of the Web portions 3 doubled over upon themselves with their points of folding constituting the inner periphery of the supporting structure. In the folded position of the sheet material, the openings 2 extend radially of the ring and provide for the doubled-over webs 8 being spaced apart in compressible relation to one another.

Received at the outer side of the supporting structure, and constituting an outer periphery therefor, are upper and lower circumferential surfaces made up of the segments or crowns B and disposed in contiguous relation to one another to comprise upper and lower layers of the sheet material. The cuts or openings 4 and 5, in the folded position of the strip, extend radially inward and provide for adjacent segments in each of the above mentioned layers, being spaced apart in compressible relation to one another.

The openings 4 of; the top circumferential surface occur ln staggered relation with respect to the openings 5 of the bottom circumferential surface indicated, and each opening is thus sealed, relative to flow of fluids vertically of the ring, by adjacent segments. Also, the openings 4 and 5 connect with openings 2 to form continuous passages, extending radially of the ring.

In the construction of a piston ring it is usually necessary to provide at the top and bottom of the ring "land surfaces," also referred to as "seating surfaces" or sealing surfaces," which ordinarily extend throughout the radial width of the ring. Such surfaces allow a ring to properly seat" or "seal" in its groove during reciprocation of the piston and thereby prevent flow of fluids past the ring.

A feature of the above indicated method of making rings is the provision of novel "land surfaces or "sealing surfaces" which provide for satisfactory seating or sealing of the ring in its groove and effect other advantages. In the ring of the invention, such surfaces are comprised by a plurality of ring-forming portions as embodied by the segments 6 and I. It has been found that by arranging the segments in contiguous relation to one another, they may comprise circumferential areas well adapted to constitute surfaces by which the ring may seal in its groove and prevent passage of oil therethrough. It also is found that the size of the segments may be such that they constitute only a part of the radial width of the ring, thus allowing the seating or sealing surfaces to occur at one side of a supporting structure or at other points. Such a sealing surface makes possible the construction of a light, efflcient ring, which at its supporting portions may be of an open construction highly adapted to facilitating passage of oil therethrough and comprising an oil metering member. Also, by making possible the construction of a suitable sealing surface from separate ring-forming portions, various arrangements and ring constructions of sheet metal are possible. The relatively smaller sealing surface of the ring effected by the ring-forming portions or segments also presents a further advantage by reason of the fact that there is reduction in extrusion of oil on to a cylinder wall such as occurs when an oil ring slaps in its piston groove. This is so for the reason that less oil can collect at the top and bottom sides of the ring.

Another feature of the method consists in providing cuts or openings arranged in overlapping relation whereby intervening sections or portions of the cut material may be bent or flexed toward one another. By this means there is effected an extensible and compressible element. This element is adapted to being formed into an annular body and thereafter to present a circumferentially extensible and contractible character as has been illustrated. In developing extensibility in this way in an annular body, a preferable result may be obtained by making those cuts or openings which are to occur at the inner periphery of the body larger than openings which are to occur at the outer periphery of the body, as for example has been done with respect to openings 2 on the one hand and 4 and 5 on the other. This improves the range of extensibility which is effected and benefits the operation of the structure as a piston ring.

It will be observed that the ring construction described presents relatively thin peripheral edges which are well suited to acting as oil metering portions and to approximating the thin edges of separate steel rings heretofore used. From the relatively small bearing surface of the ring, and its highly developed circumferentialiy extensible and contractible character described, a'very desirable range of wall pressure may be obtained which particularly suits the ring to use with worn cylinders without there developing greatly increased cylinder wear.

Still another feature of the invention consists in a ring construction which is not afiected by carbonization. It is pointed out that in substantially all oil rings, special passages are provided to pass oil to the crankcase. Such openings of any appreciable size, occurring in a ring body, tend to become clogged with carbon and fail. Carbonization takes place in two ways: first, in a thick soft body which develops rather quickly, and second, in a hard scaly mass which is formed after longer periods of ring operation. The ring of the invention presents no relatively large oil passageways in which carbon can form, and is sufllciently thin that it may depend upon passing 'oil over and under itself and through its interstices to provide efficient operation. The interstices are of a minute character and are continually flexing which further prevents any substantial carbon formation at these points.

In operation the ring functions as a gapless ring with its end adapted to abut one another. By its circumferential extensibility, the ring completely engages the wall of a cylinder, conforming to any non-uniformity or worn areas in the cylinder, and exerting a substantially uniform pressure at all points there-sloug It should be noted that the extensible character'or' the ring is attained without the use of expander members disposed between the back of a ring and its ring groove. As a result there is less transfer of piston slap, and a reduction of the gear ordinarily developing from such piston 5 ap.

With reference to specific operation of the ring structure as an oil metering member, it is pointed out that the segments 6 and 1 are contiguously arranged to constitute substantially continuous circumferential surfaces by which the ring may form a satisfactory seal against a top or bottom side of a piston groove for preventing passage of oil thereby. The thickness of the sheet metal may be varied to form a ring presenting suitably thin oil scraping edges. By the location of the relatively large openings 2 extending well out toward the segments 6 and-l. oil collected by the segments may rapidly be passed over the ring into the ring groove and then down into the crankcase.

Various advantages'are present in connection with the method of making piston rings illustrated in Figs. 1-8 inclusive. There is provided a one-piece ring which is adapted to be easily handled and assembled about a piston. The ring is provided with a novel extensible and compressible character, rendering it particularly adapted to conforming to worn or irregular-'cyllnder surfaces. The procedures indicated may be utilized to provide thin oil scraping edges of a character closely simulating the thin edges of separate C-type rings heretofore employed. The entire structure is adapted to be formed of a tough thin material as steel of which only relatively small amounts are required, to provide a light durable ring. In addition, materials of the character indicated, and the composite construction developed in connection therewith, are highly adapted to cheap manufacturing processes which make use of conventional tool machinery such as punches, forming and shearing dies, and press and rolling mechanism whereby relatively smaller amounts of money are required to be invested in tooling up" to make the rings, and relatively smaller investments are required to be maintained at any one time. By the construction shown, almost any desired'wall pressure may be arrived at without reducing the uniformly extensible character of the ring, and in addition it is possible to provide an improved and increased range of expansibility at any point in which the wall pressure of the ring is satisfactorily operative. The ring is further characterized by efficient oil metering and suitable repassing of oil to the crankcase, and provides such functions with substantial elimination of cylinder wear. I

While the particular forming steps illustrated have been shown in connection with a length or strip of material, it is intended that such operations may be effected upon materials of varying cross section occurring in varying forms as in sheet form or in a web or roll and of. one or more thicknesses. The cutting or forming operations may be modified as for instance in the manner indicated in Fig. 4, in which alternately disposed slits or cuts 8 are employed in place of the openings shown in Figs. 2 and 3. Still other changes in the arrangement of the openings or cuts may be resorted to, as for example, openings may be disposed diagonally or angularly of a strip of vide ring-forming portions'which are completely severed and adapted to be separately brought together piece by piece on some form of annular supporting structure. The various advantages obtained by any one or all of the operations described may be resorted to in difierent ways and for different purposes in the modification of the ring other than the oil control type referred to, as for example compression rings or expander rings or other special types of sealing members.

A development in oil control ring construction is a ring assembly made up of a plurality of thin C-type rings mounted one upon another and provided with an expander member engaged at the inner side of each of the rings. Such a construction has been found to function due to a hydraulic pressure set up at the outer periphery thereof when the ring assembly reciprocates against the wall of a cylinder and collects oil between its sections. The hydraulic pressure opens the rings up upon one another and thereby provides passageways for the oil to move inwardly of the ring. A general objection to such rings is that they require a relatively strong expander, which undesirably wears the cylinder wall. Also, in order that the hydraulic pressure may be effective in spacing the rings apart, it

utilize the cutting or forming operations to promust first overcome the friction of the rings on the expander member and a part of its value is lost thereby.

In accordance with the present invention,-

there is provided a ring assembly as illustrated in Fig. 10, in which the desirable hydraulic pressure of the conventional ring above described, is retained and the objections present from the use of an expander are eliminated. In addition,

further improved functioning is obtained by modification of the structure. 4

.The assembly shown in Fig. 10 consistsof a cylinder 9 and piston to in which are mounted two ring sections H and I2 disposed loosely one upon the other. These ring sections constitute clrcumferentialiy extensible and compressible annular bodies of the same general character as the rings described in Figs. 1-8, inclusive. However, the method of forming the ring sections is. V

through oil passages IS in the piston i0.

It is pointed out that the present assembly, while functioning in the same manner as the hydraulic rings above referred to, is an improvement thereupon by reason of there being no separate expander member present; also by reason of the fact that there are radial interstices extending between the inner and outer peripheries of each ring section; and also due to each ring section being made up of upper and lower layers secured together along one side thereof. In use, the ring assembly possesses the advantage of being very easily mounted in a piston, independently of any expander member. Also, by the elimination of the expander member, their ability to be forced apart byoll pressure during reciprocation against the wall of a cylinder is greatly increased, repassing of oil is .facilitated, and cylinder wear avoided.

Fig.ll illustrates a modified method of inaking a ring in which specific changes in the fold ing operation above described are carried out. A strip of the sheet metal, formed in some suitable manner as has for example been illustrated in Figs. 2 and 3, is folded longitudinally as before but in this instance reversely upon itself to form an increased number of layers of material, piled one upon another to make up the ring l2a. Several changes are effected in the character of the ring by this modified folded construction. The height of the ring is increased, the effective size of the interstices becomes greater, the wall pressure of the ring is increased, and other advantages as above are effected.

The method of reversely folding sheet metal into a number of layers as shown in Fig. 11 may be further modified as illustrated in Fig. 12 in which two of the folds are left in a spaced apart position to comprise the ring 1217. By this construction, there is effected vertical resiliency or "take up" in the ring, enabling it to engage with opposite sides of a piston ring groove and thereby eliminateslapping of the ring in the groove.

In Figs. 13-16, inclusive, there has been illustrated another general type of method for making piston rings which is further exemplary of changes in procedures and which particularly relates to the forming of circumferential oil scraping edges integral with and extendingbeyond a supporting structure therefor. In the fig ures referred to, a sheet metal material is again employed and subjected to some desirable forming operation, such as has been indicated in Figs. 2 and 3, to provide segments or ring-forming portions I1 and I8, interstices Fla and I Be, openings IO, and webs l9a. In this case the formed material is folded into an' open annular body as for instance of the U-shaped formation as shown in Figs. 4 and 5. By this procedure there is efi'ected a circumferentially extensible and contractible annular supporting structure at the outer periphery of which extend spaced-apart upper and lower circumferential oil scraping edges made up of the segments or ring-forming portions l1 and I8.

It will be seen that this ring construction has all of the advantages heretofore noted with respect to punched or folded sheet metal ring constructions, and in addition'it presents radially extending circumferential edges which are integral with a supporting structure and 'are an improvement upon separate edges as effected by separate C-type rings heretofore described. In addition, the structure is of a highly open reticulated character, admirably suited to allowing passage of oil therethrough, either radially or vertically, with there being maintained ample circumferential sealing surface at the top and bottom sides of the ring and with the web portions Ha presenting a minimum surface area upon which carbon can form in a detrimental manner.

Figs. 17-21, inclusive, relate to another modified method of treating sheet material in which the sequence of operation heretofore described is modified. In accordance therewith a strip 20 is directly formed into a longitudinally folded member 2| as illustrated in Fig. 18. Thereafter one or the other of the cutting steps previously resorted to may be carried out on the folded member 2! as has for example been carried out in Fig. 19 to form a reticulated supporting structure of spaced-apart webs 22. Fig. 20 illustrates a further cutting operation of effecting segments 23 from interstices 28a. This procedure provides a ring as shown in Fig. 21 which is similar to the ring previously indicated in Figs. 15 and 16.

The method of Figs. 17-21, inclusive, is intended to be generally illustrative of various other methods in which sheet material is first folded and then formed by cutting or other operations. As another example there may be pointed out the method of similarly treating sheet metal folded in the manner indicated in Figs. 5 and 6. Fig. 22 is intended to specifically illustrate folding sheet metal upon itself in a longitudinal manner to form a member as 24 and thereafter cutting at points such as those indicated in dotted lines.

The method of forming a ring structure with circumferential edges which extend from their supporting structure to constitute oil scraping portions may be further modified to include the reverse folding operations indicated in Figs. 11

and 12. Fig. 23 is illustrative of such a modified procedure which results in a ring 25. Still further modification in the method referred to may be practiced as illustrated in Figs. 24 and 25 in which openings 26 and 21 are formed of different proportions. For example, as shown the openings 28 do not extend into the top or bottom sides of the finished ring.

In the methods described and illustrated, the cutting or other type of forming operations carried out on the sheet metal have in all cases effected the extensible character of the resulting ring. The cutting operations referred to may be employed for other purposes not limited to the imparting of the flexibility described, In Figs. 26-35, inclusive, another general type of method of making piston rings is illustrated which is particularly exemplary of cutting ring portions in sheet material independently of creating flexible character, and of forming piston rings in which flexibility is entirely derived from folding operations.

Having reference to Figs. 26435, inclusive, 2! denotes a strip of material which is cut in some suitable manner as by punching to provide segments 3!] and cuts 3| extended inwardly of the segments. This formed strip is then folded transversely of the strip in the manner illustrated in Fig. 28 to comprise a supportin structure made up of web portions 32, at the outer side of which and at the top and bottom thereof, are disposed the segments 3! with the web portions being folded away from the segments in accordance with the clearance provided by the slits 3|. Figs. 29 and 30 illustrate a continuance of the reversely folding operation to form piston rings in which the webs are arranged in varying position, as for instance the vertical position assumed in Fig. 29 or the angular position as indicated in Fig. 30. The webs are in substantially spaced relation as illustrated in Figs. 31 and 32 in which finished rings are illustrated.

It will be seen that there are thus effected upper and lower circumferential edges, made up of a plurality of ring-forming portions or segments arranged in. contiguous relation to one another and supported in a circumferentially extensible and contractible manner. As described in the previous ring constructions, ring-forming portions 30 are arranged to make up circumferential sealing surfaces for the ring and there is effected an open supporting structure for receiving the segments, at one side thereof. It should be observed that there is thus illustrated still another modification of a cut and folded sheet metal piston ring, in which the results obtained by the cutting and folding operations are interchanged and the cutting is further helpful in determining the points along which folding occurs in relation to the ring-forming portions or segments.

A modification in the method of transversely folding a strip of material is illustrated in Figs. 33 and 3%, in which a strip 33 is formed, at opposite sides thereof, with segments 3d and 35 disposed in staggered relation with respect to one another. The strip at this point may also be provided with oil passages 35, if so desired. The formed member is then reversely folded upon itself, as before into an annular body of extensible and contractible character, made up of webs 37. However, the method of forming the folded strip into an annular body is such as to arrange the lines of folding so that they extend in a direction vertically of the annular body. In this form, the segments 36 and 35 project from the top and bottom of the annular structure and the final step in the method is to bend the segments 36 downwardly and away from the supporting structure and the segments 35 upwardly and away from- This procedure is intended to be illustrative of.

steps in which folding may occur in various planes with respect to the sheet material.

it will be observed that there have been dis closed and described ring members broadly illus- 'sembling procedures are subject to modification in various ways and for various purposes, and are intended to be practical in connection with making' various types of piston rings. The improvements disclosed provide novel, cheap, light, efiicient and durable ring structures. It is pointed out that there is made available a method of making piston rings highly adapted to being carried out with tool machinery, which greatly lowers the cost of manufacturing piston rings generally and makes for more efllcient production of such rings.

While I have shown preferred embodiments of the invention, it should be understood that vari- 0113 changes and modifications may be resorted to in connection therewith, as for example proc'edures for forming and assembling any type of composite ring structures may be resorted to in keeping with the spirit of the invention as delined by the appended claim.

Having described my invention, I claim:

That improvement in methods of making oil control piston rings which comprises cutting spaced openings elongated transversely in a flat strip of piston ring material at points intermediate the edges thereof and forming transverse cuts through the opposite edges of the strip to connect with said openings, said transverse cuts being of less width than said openings to provide sealing portions occurring alternately at opposite edges of the strip and intermediate supporting Y portions for the sealing portions, bending said trative of methods of forming composite piston ring structures from sheet material in which separate ring=forming portions are devised and brought together. It is also pointed out that a novel combination of cutting operations and folding operations has been described to produce novel ring structures, ring surfaces, and ring functions. Each of the several forming and as= supporting portions along a line of bending which 

